btCudaBroadphase is some R&D work, a first attempt to use CUDA in Bullet.
It uses the NVidia CUDA particle demo grid broadphase as Bullet broadphase.

Press 's' to toggle between the original CUDA particle demo and using Bullet+btCudaBroadphase.
Press '1', '2','3','4' for different start configurations.
Right click for options menu.

See some related discussion here:
http://www.bulletphysics.com/Bullet/phpBB3/viewtopic.php?f=9&t=500&start=105


Get NVidia CUDA from here:
http://www.nvidia.com/object/cuda_get.html